1. Field of the Invention
The present invention relates to illuminating devices having a taper-like imitation flame for decorating purposes.
2. Description of the Prior Art
It has been proposed, as a taper-like imitation flame, to use a flame-shaped envelope instead of the conventional spherical glass envelope of the incandescent lamp and to mount it on a taper post with a candlestand. This type of illumination lamp is aimed to be used singly or a few lamps are used at a time. However, due to the shape or appearance, the use of such lamp is much limited and is not suitable for illumination in a room or for window display. Also, the lamp itself is not an ordinary lamp and it necessarily uses special wiring or connecting means for power supply, and therefore the use thereof has been further limited. On the other hand, in order to use many lamps at a time in a chandelier, it has been proposed to apply a base shell to the bottom end of the taper post and to use a separate cover over a smaller but ordinary incandescent lamp in Japanese Utility Model Registration No. 729,931. According to this lamp, the imitation effect of the envelope was not sufficient. In other words, when the lamp is lit, the envelope thereof really shows the flame shape. However, its light source is still static and cannot show a taper like glimmering or flickering flame. Further, since the outer shape is so distinct, its imitation effect has been rather poor.
In this connection, in order to obtain better imitation effect, it has been proposed that the outer surface of the flame-shaped cover is arranged to be closely wound with fine glass fibers and to be adhered and fixed, as shown in U.S. Pat. No. 3,127,295, thereby moderating the distinct outer shape. In order to lessen the manufacturing cost for the above type of lamp, it has been further proposed, in Japanese Utility Model Publication No. 37403/1972, that the cover is formed in two axially separate portions by molding synthetic resin and, at the time of molding, concentric stripes or a spiral line are, or is, formed around the inner surface of the cover.
It has been proposed, in Japanese Utility Model Laid-open No. 150580/1974, that a light source bulb, such as a torpedo shaped bulb, is covered by a evacuated globe bulb. In these conventional examples using covers over electric bulbs, since the electric bulbs are incandescent lamps and covers are applied thereover, there has occurred a problem of heat dissipation and the lighting life, ordinarily of 1200 - 1800 hours, will be shortened. Especially the lighting life of the evacuated globe type bulb will be shortened to half of the ordinary lighting life. As a result, when many lamps are used, bulbs must be exchanged often, thus making these kinds of lamps improper to be used in a chandelier or other illumination means suspended from a ceiling or supported in the show window. Such repeated exchanging of bulbs in these cases is very troublesome.
As a special decorative lamp, there has been proposed, in Japanese Utility Model Registration No. 411644, a neon lamp wherein neon discharge electrodes of a peculiar shape are used in a radiation part of the lamp and discharge arc between the opposing electrodes is made to unstably move to and fro from time to time. In this case, however, the discharge electrodes are plate-shaped and face each other, and therefore although the light source is seen from the facing side as a facial light, from the side of the electrodes, light is seen as a mere arc between the two line-form electrodes. Further, when the neon lamp is mounted by rotating its screwed base into the socket, the direction of light source is not constant. Since the move in the radiation part is too frequent, when many lamps are used simultaneously, visual flickers are large so as to obstruct the usage in a chandelier. Further, since the discharge thereof is very unstable, and its discharge portion moves frequently, brightness is weak and much illumination effect is not expected.